The present invention relates to the field of mixing solid particles with a liquid such as water. More particularly, the invention relates to an apparatus and method for expediting mixing processes between a liquid and fine solid particles such as dry polymer.
In the oil and gas, petrochemical and manufacturing industries, dry powdered materials such as polymeric compounds are transported to a well site or other field locations to reduce shipping weight and to facilitate material handling procedures. After the dry material arrives at the site, the dry material must be hydrated with a liquid such as water to form the desired compound. Such compounds can comprise drilling, fluids, water clarifiers, flocculants, fracing gels, cements, and other useful compounds. To save transportation costs, the hydrating operations can also be conducted within industrial, commercial or construction locations after the dry material has been transported.
One area involving the hydration of dry powdered materials comprises the hydration of polymers. When polymer particles are mixed with a liquid such as water, the outer portion of the polymer particles wet instantaneously on contact, while the center remains unwetted. The outer wetted surface area forms a viscous shell which can restrict the wetting of the particle center. These partially wetted or unwetted particles are known as "fisheyes", and can be processed with mechanical mixers to reduce the unwetted particles into a homogeneous wetted mixture. However, mechanical mixing requires energy, degrades the molecular bonds of the polymer, and reduces the effectiveness of the polymer for the intended use. Consequently, a need exists for improved mixing systems that can effectively wet dry particles such as polymers without degrading such polymers.
Various techniques have been developed to hydrate dry polymeric powders. In U.S. Pat. No. 3,902,558 to Watson, Jr. (1975) and in U.S. Pat. No. 4,014,527 to Watson, Jr. (1977), polymer was sprayed through a nozzle against a sheet of water to contact and blend the polymer with the water. In U.S. Pat. No. 4,077,612 to Ricciardi (1978), a mixing chamber fed atomized polyelectrolyte particles into a turbulent, cyclonic water stream to create a turbulent wetting action. In U.S. Pat. No. 4,664,528 to Rodgers et al. (1987), an emulsion polymer was mixed with a conventional static mixer and was moved with various circulation means. In U.S. Pat. No. 4,688,528 to Brazelton et al. (1987), dry polymer was fed into a mixing chamber having a mechanical impeller, and the mixture was then moved to a lower aging chamber. In U.S. Pat. No. 4,764,019 to Kaminski et al. (1988), a two stage mixing tank system having a variable speed auger in the secondary mixing tank. In U.S. Pat. Nos. 4,845,192 and 4,874,588 to Sortwell et al. (1989), high shear forces were introduced on a dry polymer as water was introduced into a cyclone mixing device. In U.S. Pat. No. 5,344,619 to Larwick et al. (1994) a vortex chamber was used to mix dry polymer particles with water, and a mechanical agitator operated within a tank. In U.S. Pat. Nos. 5,372,421 (1994) and 5,470,150 (1995) to Pardikes, a polymer was mixed with water and the pressure was reduced to relax the polymer mixture.
Conventional mixing systems require significant energy, mechanical mixing and aging time to achieve a desired degree of particle hydration. Although such systems can be effective for certain types of dry powders, such the effectiveness of such systems is limited for dry powdered materials such as polymeric compounds. Accordingly, a need exists for an improved system which effectively and efficiently hydrates dry particles.